Interface systems for use in transferring heat produced from a heat-dissipating electronic component to a heat dissipator or heat sink are well-known in the art. In this regard, such electronic components, the most common being computer chip microprocessors, generate sufficient heat to adversely affect their operation unless adequate heat dissipation is provided. To achieve this end, such interface systems are specifically designed to aid in the transfer of heat by forming a heat-conductive pathway from the component to its mounting surface, across the interface, and to the heat sink.
Exemplary of such contemporary thermal interfaces are THERMSTRATE and ISOSTRATE (both trademarks of Power Devices, Inc. of Laguna Hills, Calif.). The THERMSTRATE interface comprises thermally conductive, die-cut pads which are placed intermediate the electronic component and the heat sink so as to enhance heat conduction therebetween. The THERMSTRATE heat pads comprise a durable-type 1100 or 1145 aluminum alloy substrate having a thickness of approximately 0.002 inch (although other aluminum and/or copper foil thickness may be utilized) that is coated on both sides thereof with a proprietary thermal compound, the latter comprising a paraffin base containing additives which enhance thermal conductivity, as well as control its responsiveness to heat and pressure. Such compound advantageously undergoes a selective phase-change insofar the compound is dry at room temperature, yet liquifies below the operating temperature of the great majority of electronic components, which is typically around 51.degree. C. or higher, so as to assure desired heat conduction. When the electronic component is no longer in use (i.e., is no longer dissipating heat), such thermal conductive compound resolidifies once the same cools to below 51.degree. C.
The ISOSTRATE thermal interface is likewise a die-cut mounting pad that utilizes a heat conducting polyimide substrate, namely, KAPTON (a registered trademark of DuPont) type MT, that further incorporates the use of a proprietary paraffin based thermal compound utilizing additives to enhance thermal conductivity and to control its response to heat and pressure. Advantageously, by utilizing a polyimide substrate, such interface is further provided with high dielectric capability.
The process for forming thermal interfaces according to contemporary methodology is described in more detail in U.S. Pat. No. 4,299,715, issued on Nov. 10, 1981 to Whitfield et al. and entitled METHODS AND MATERIALS FOR CONDUCTING HEAT FROM ELECTRONIC COMPONENTS AND THE LIKE; U.S. Pat. No. 4,466,483, issued on Aug. 21, 1984 to Whitfield et al. and entitled METHODS AND MEANS FOR CONDUCTING HEAT FROM ELECTRONIC COMPONENTS AND THE LIKE; and U.S. Pat. No. 4,473,113, issued on Sep. 25, 1984 to Whitfield et al. and entitled METHODS AND MATERIALS FOR CONDUCTING HEAT FROM ELECTRONIC COMPONENTS AND THE LIKE, the contents of all three of which are expressly incorporated herein by reference.
The prior art practice of adhesively bonding a thermal interface to either the electronic component or the heat sink is likewise well known. Such practice facilitates handling and expedites installation of the interface, as well as allows the heat conductive interface to be sold along with either the electronic component or the heat sink already in place thereupon.
According to contemporary practice, however, the use of an adhesive material to attach the heat conductive interface to either the electronic component or the heat sink is generally undesirable. In this regard, by introducing an additional layer to the interface system, namely in the form of adhesive, the ability of the interface to conduct the flow of heat thereacross is substantially reduced. As those skilled in the art will appreciate, the addition of a layer of material to an interface system, which is already typically comprised of multiple-layer construction, contributes three distinct impediments to heat flow, namely, each layer introduces the material of which the layer itself is comprised across which the heat must be conducted, as well as creates two interfaces at either surface of the layer.
Thus, it will be appreciated that it is highly desirable to minimize the number of layers, and consequently the number of interfaces, comprising an interface system. Along these lines, it has been found that the use of a thermal interface having six layers does not provide desirable heat transfer from a given electronic component to the heat sink coupled therewith. The use of an adhesive, and more particularly a layer thereof, for affixing an interface system in position between electronic component and heat sink further contributes to such inefficiency by introducing yet another layer at the interface between the electronic component and the heat sink which, as a consequence, substantially impedes heat flow. Accordingly, there has been and continues to exist a recognized problem of finding methods to securably mount such interface systems in fixed position between an electronic component and a heat sink, particularly through the use of adhesives, without such adhesive layer extending across or otherwise obtruding upon the interface surface across which heat is conducted. In addition, it should further be noted that from a practical standpoint, the manufacturing of such interface systems having multiple layers is expensive, and to add yet another layer further adds to an already considerable expense.
There is therefore a need in the art to provide a a thermal interface having a minimal number of layers and provides adequate heat dissipation but further utilizes an adhesive to attach the interface to either one of the electronic component or the heat sink coupled therewith. There is a further need in the art to provide a thermal interface which is adhesively bondable to either an electronic component or the heat sink coupled therewith which further does not substantially increase the manufacturing cost thereof as compared to contemporary thermal interface pads.